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A new method to determine the spin tune is described and tested. In an ideal planar magnetic ring, the spin tune-defined as the number of spin precessions per turn-is given by ν s ¼ γG (γ is the Lorentz factor, G the gyromagnetic anomaly). At 970 MeV=c, the deuteron spins coherently precess at a frequency of ≈120 kHz in the Cooler Synchrotron COSY. The spin tune is deduced from the up-down asymmetry of deuteron-carbon scattering. In a time interval of 2.6 s, the spin tune was determined with a precision of the PRL 115, 094801 (2015) P H Y S I C A L

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Spin-dependent totalpd cross sections are considered using the optical theorem. For this aim the full spin dependence of the forwardpd elastic scattering amplitude is considered in a model independent way. The single-scattering approximation is used to relate this amplitude to the elementary amplitudes ofpp andpn scattering and the deuteron form factor. A formalism allowing to take into account Coulomb-nuclear interference effects in polarizedpd cross sections is developed. Numerical calculations for the polarized totalpd cross sections are performed at beam energies 20-300 MeV using theNN interaction models developed by the Jülich group. Double-scattering effects are estimated within the Glauber approach and found to be in the order of 10-20%. Existing experimental data on differentialpd cross sections are in good agreement with the performed Glauber calculations. It is found that for the usedNN models the total longitudinal and transversalpd cross sections are comparable in absolute value to those forpp scattering.

This Letter reports the successful use of feedback from a spin polarization measurement to the revolution frequency of a 0.97  GeV/c bunched and polarized deuteron beam in the Cooler Synchrotron (COSY) storage ring in order to control both the precession rate (≈121  kHz) and the phase of the horizontal polarization component. Real time synchronization with a radio frequency (rf) solenoid made possible the rotation of the polarization out of the horizontal plane, yielding a demonstration of the feedback method to manipulate the polarization. In particular, the rotation rate shows a sinusoidal function of the horizontal polarization phase (relative to the rf solenoid), which was controlled to within a 1 standard deviation range of σ=0.21  rad. The minimum possible adjustment was 3.7 mHz out of a revolution frequency of 753 kHz, which changes the precession rate by 26  mrad/s. Such a capability meets a requirement for the use of storage rings to look for an intrinsic electric dipole moment of charged particles.

A recent cross section measurement of the deuteron breakup reaction pd → (pp)(0 • )+ n(180 • ), in the GeV region in a kinematics similar to backward pd elastic scattering, strongly contradicts predictions of a pd → dp model based on the one-nucleon exchange, single pN scattering and ∆ excitation mechanisms, and on the wave functions of the Reid soft core and Paris N N potentials. We show within the same model that for the CD Bonn N N potential there is qualitative agreement with the data. It is attributed to a reduction of the one-nucleon exchange at energies above 1 GeV and an increase of the ∆(1232)-isobar contribution, both related to the short-range properties of the wave functions generated by this potential.